Shapefiles

A shapefile is a simple, non-topological vector format for storing the geometric location and attribute information of geographic features.

Shapefiles spatially describe geometries such as points, lines, and polygons, which represent geographical features such as the epicenter of an earthquake, hurricane storm tracks, wind speed footprints, and state boundaries. For example, you may have your own surveyed flood or earthquake data that has been saved in a shapefile format. A valid shapefile includes several component files that contain geometric and attribute data.

Note:

The data conversion examples used in the topic are based on the use of ESRI's ArcGIS tools for converting the GIS files. However, you can use other GIS tools to prepare the GIS files for importing spatial data into Touchstone, such as: QuantumGIS (QGIS), GDAL/OR (command line only), and Clark Labs IDRISI.

The following component files are required and must be stored in the same project workspace.

  • SHP: The main file, which you select during the import process. This file contains information about the shapes (geometries) and locations of geographic features.

  • DBF: The database table that stores the attribute information for each shape in the shapefile. For example, this file can contain place names, latitude and longitude coordinates, magnitudes for earthquake objects, and wind speeds for hurricane-related objects.

  • SHX: The positional index of the feature geometry (the SHP file) that supports quick seeking forwards and backwards.

For each component in the shapefile, the maximum size is two gigabytes.

The base name of the required files must be the same. For example: USstates.shp and USstates.dbf.

There are several ways that you can use imported shapefiles; for example, you can import the following types of shapefiles:

  • Polygons for specific hazard zones or areas, such as Florida Wind Mitigation Zones

  • Polygons for boundaries, such as territories or administrative areas

  • Polygons that identify the area or footprint affected by a given event, such as those included in Verisk ALERT posts for the Oklahoma tornados, European floods, and Colorado fires.

    Note:

    Verisk ALERT Worldwide provides recent catastrophe information and speedy access to posted event sets.

  • Polylines for measuring the distance to specific hazards (fault lines or coastlines) or events; for example, for measuring events such as hurricane storm tracks

  • Points for measuring the distance to specific hazards or events, such as to the position of an earthquake's epicenter, or to terrorism events